1. Field of the Invention
Example embodiments relate generally to nuclear reactors, and more particularly to a method and apparatus for a Boiling Water Reactor (BWR) jet pump three point slip joint clamp used to prevent leakage and vibration while constraining an interface between the inlet mixer and diffuser of a BWR jet pump assembly.
2. Related Art
A reactor pressure vessel (RPV) of a boiling water reactor (BWR) typically has a generally cylindrical shape and is closed at both ends (for example by a bottom head and a removable top head). A top guide typically is spaced above a core plate within the RPV. A core shroud, or shroud, typically surrounds the core and is supported by a shroud support structure. Particularly, the shroud has a generally cylindrical shape and surrounds both the core plate and the top guide. There is a space or annulus between the cylindrical reactor pressure vessel and the cylindrically shaped shroud.
In a BWR, hollow tubular jet pumps positioned within the shroud annulus provide the required reactor core water flow. The upper portion of the jet pump, known as the inlet mixer, is laterally positioned and may be supported by conventional jet pump restrainer brackets. While conventional jet pump restrainer brackets may provide system stiffness that mitigates vibration of system components, slip joint leakage flow induced vibration (SJLFIV) may still occur between the inlet mixers and the diffusers. Slip joint leakage FIV causes high vibratory loads, which have been identified as a root cause of jet pump assembly vibration damage.
Conventionally, many attempts have been made to reduce slip joint leakage FIV. For instance, auxiliary wedges at the set screws of restrainer brackets, labyrinth seals, restrainer bracket pad repair, slip joint clamps and replacement main wedges have all been used. While these conventional solutions have provided some additional system stiffness, none of the solutions mitigate leakage and vibration at the actual slip joint interface without placing additional loads on the slip joint interface between the inlet mixer and the diffuser. In particular, conventional slip joint clamp designs have mitigated vibration, though they have increased the overall load being placed on the slip joint interface.